1. Field of the Invention
This invention relates to a flight motion simulator for testing an inertial guidance control system that simultaneously simulates rotational and translational movement of a unit under test in three orthogonal axes.
2. Description of the Prior Art
Motion simulators are utilized to produce fore and aft, lateral, elevational, roll, pitch and yaw movements or any combination of such movements to test guidance control systems used in missiles, satellites and the like. A known six degree of freedom simulator, as disclosed in U.S. Pat. No. 3,295,244, comprises three mutually perpendicular axes of linear movement and three axes of rotational movement, one of the axes being normal to the other two. A platform is supported above a base by six powered and linearly controlled actuators. Each actuator extends between the platform and the base to provide vertical linear translation and pitch and roll motions of the platform.
U.S. Pat. No. 3,449,843 discloses a light weight six degree of freedom simulator for zero gravity study. The simulator includes a base levitated by air bearing pads on a smooth floor. The bearing pads provide two degrees of translational freedom in a horizontal plane and one degree of rotational freedom about a vertical axis. Extending upwardly from the three-legged base is a column on which is mounted a pair of bearings and an elongated parallelogram. A seat assembly is mounted on the parallelogram to translate vertically therewith. This arrangement provides three degrees of translational freedom and three degrees of rotational freedom of the motion simulator.
It is also known in inertial instrumentation to support gyroscopes and accelerometers by means of electrical fields. For example, an inertial member in the form of a perfect sphere is maintained centered precisely at the center of an electrode support structure. Electric fields are established by a set of electrodes forming a spherical envelope about the inertial member. Three pairs of electrodes are utilized to generate electrical support fields along one of three orthogonal axes. U.S. Pat. No. 3,954,024 discloses an inertial support in which three pairs of electrodes are utilized and in the event the inertial member is not perfectly centered, a closed loop servo control restores a conductive sphere to a centered position between support electrodes.
U.S. Pat. No. 3,697,143 discloses an electrostatically supported gyroscope in which a conductive ball is supported between pairs of electrodes. A suspension utilizes a plurality of amplifiers for sensing the voltage difference between electrodes of a pair. A control system detects displacement of the ball with respect to the electrode pair. A displacement signal is generated to apply a charge to the electrodes in a direction and with a force for restoring the ball to a centered position between the electrodes. It is also known, as disclosed in U.S. Pat. No. 4,511,190 to utilize magnetic bearings for controlling the attitude of artificial satellites.
While it is known to utilize electrostatic and hydraulic means for supporting a unit under test in a motion simulator, the known motion actuators are limited in the response time of the actuator to generate the required motion upon actuation. Conventionally, with a unit under test supported in a gimballed system, the natural resonant frequency of the gimballed system limits the bandwidth that is achievable to about 75 Hz. Therefore, there is need for a motion simulator that efficiently simulates vibration characteristics at frequencies greater than the frequencies achievable by conventional torque actuators.